1. Field of the Invention
The present invention relates to load control devices for controlling the amount of power delivered to an electrical load from a source of alternating-current (AC) power, and more particularly, to a wall-mountable electronic timer for supplying power to a connected electrical load for a predetermined amount of time selectable by a user.
2. Description of the Related Art
In response to increasing awareness of energy conservation, many lighting control devices, such as dimmers, electronic timers, occupancy sensors, and daylight sensors, provide means for energy management of lighting loads in commercial and residential installations. Specifically, electronic timers operate to turn off a connected electrical load after a predetermined amount of time after the electrical load is turned on. Typically, the electronic timer includes a switching device, such as a relay, coupled in series electrical connection between an AC power source and the electrical load. Often, electronic timers are adapted to be mounted in electrical wall-boxes and are used in rooms, such as bathrooms, where a light or an exhaust fan may be turned on when the room is first in use, and left on after the room is no longer in use.
One prior art wall-mounted electronic timer is the Decora® electronic timer (e.g., part number 6515M) manufactured by Leviton Manufacturing Co., Inc. The electronic timer comprises four buttons, each corresponding to a different timeout period, e.g., two minutes, five minutes, ten minutes, and fifteen minutes. The buttons are each labeled with the corresponding timeout period. Actuating one of the four buttons turns a connected electrical load on and begins a countdown with the corresponding timeout period. After this period of time expires, the electrical load is turned off. A visual indicator, e.g., a light-emitting diode (LED), is located next to or in each of the buttons and illuminates to indicate how much time is left in the timeout period. For example, if there are nine minutes left until the lighting load is turned off, the visual indicator corresponding to the timeout period of ten minutes will be illuminated. During the last few minutes, e.g., the last two (2) minutes, of the timeout period, the visual indicator next to the bottom button blinks quickly. Further, the electronic timer has an off button located below the other four buttons. When the off button is actuated, the electrical load is immediately turned off.
Another wall-mounted prior art electronic timer is an electronic in-wall countdown timer (part number EI210) manufactured by Intermatic Incorporated. This electronic timer has a single button and four visual indicators located in a linear array on a front surface of the timer. Selectable timeout periods are listed beside the visual indicators and include ten minutes, fifteen minutes, thirty minutes, and sixty minutes. Repeatedly pressing the single button cycles the electronic timer between the four different timeout periods and causes the corresponding visual indicator to illuminate. Pressing and holding the single button causes the electronic timer to enter a bypass mode, i.e., the timing function is disabled and the timer will supply power until manually turned off. A fifth visual indicator, which is located below the other four visual indicators, is illuminated when the electronic timer is in the bypass mode.
However, typical prior art electronic timers have user interfaces that provide limited functionality, require a high level of cognition to operate, and have an unsatisfactory aesthetic appearance. For example, the Leviton electronic timer does not offer a bypass mode. With the Intermatic electronic timer, a user must repeatedly press the single button to turn an electrical load on with a long timeout period or to turn off the lighting load. Further, the functional buttons and visual indicators of typical prior art electronic timers are not attractive, especially in a residential installation. Also, prior art electronic timers typically look much different than other lighting controls, such as switches and dimmers, that might be ganged next to the electronic timer.
Some electronic dimmers, such as, for example, the Maestro® smart dimmer, have offered a user interface that allows access to many features, is easy to use, and provides an attractive appearance. The Maestro® dimmer is described in greater detail in U.S. Pat. No. 5,248,919, issued Sep. 29, 1993, entitled LIGHTING CONTROL DEVICE, the entire disclosure of which is hereby incorporated by reference.
Therefore, there is a need for an electronic timer having a simple user interface that provides an attractive appearance, is easy to use, and allows access to many features.